After Updating to version 1.4.6 [bbddab7675] I got the following warning:

'WARNING: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/var/lib/php5) is not within the allowed path(s): (/var/www/web219) in /var/www//html/album_xxxxxxxx/zp-core/functions-basic.php on line 154'
stands for my username and 'xxxxxx' for the name of the album on the server.

I added in the file /zp-core/function-basic.php the following code above line 154 to patch at the moment the problem:
'@ini_set('session.save_path', '/var/www/

open_basedir restriction indicates normally a (security) setting of your server being involved here. Best contact your host about that as well.

Also please see part of this older topic: http://www.zenphoto.org/support/topic.php?id=933706#post-1332330